OAKLAND, Calif. -- Derek Norris wasn't too surprised to hit a three-run home run on a 3-0 count in the first inning.

The Athletics catcher was only mildly shocked when he did the same thing the next inning, in nearly the exact same situation with the same count and on the same pitch.

Norris hit a pair of three-run home runs off Nationals starter Gio Gonzalez to back Scott Kazmir's fifth win and Oakland beat Washington 9-1 on Sunday to complete a series sweep.

"They've given me the green light a few times this year and it just hasn't really worked out the way it did today," said Norris, who drove in a career-high six runs.

"Everyone knows (Gonzalez) has good stuff and you have to get on him early. It just happened to work out a little bit better than it initially was planned out to be, not once but twice."

Both of Norris' home runs came on identical two-out pitches from Gonzalez, who pitched four seasons in Oakland. The two players were part of a 2011 trade between the teams.

In the lineup because of a left-hander on the mound, Norris blasted a 3-0 pitch from Gonzalez over the wall in left with two outs in the first.

Oakland led 4-0 when Norris came up in the second, again with two runners on. Gonzalez (3-3) ran the count to 3-0 before Norris hammered the ball down the left field line for his fourth home run this season.

"They had the same feel to them, same swing," A's manager Bob Melvin said. "Obviously the two swings of the bat put the game in completely different context. He has that ability."

It's the first multi-homer game of Norris' career. The six RBIs are tied for the most by an Athletics catcher since 1914.

That it came on Mother's Day and against his former team made it more memorable for Norris.

"It was one of those special days," Norris said. "I've never hit two home runs in a game. It still feels surreal."

Nick Punto added two hits and three RBIs while Brandon Moss singled twice and doubled. Oakland has won four straight since dropping five of six against Boston and Seattle.

Kazmir (5-1) bounced back from his first loss of the year to pitch seven scoreless innings while allowing only four hits. He struck out four and didn't walk a batter for the fourth time this season.

The A's completed their majors-leading fourth series sweep with another blowout of the Nationals. Oakland, which shut out Washington in the series opener, outscored Washington 21-4.

Punto added an RBI single in the first and a two-run double in the seventh.

It was a rough return to the Coliseum for Gonzalez, who pitched for the A's for four years and was making his first start against his former club. Washington's left-hander labored through 4 1/3 innings and gave up seven runs and nine hits. He struck out four and walked three in his worst outing in Oakland since giving up 11 earned runs to Minnesota on July 20, 2009.

Gonzalez was also caught on TV yelling at a teammate in Washington's dugout after the second. Earlier in the inning, the Nationals allowed a high pop-up by Yoenis Cespedes to fall to the turf and roll foul. Cespedes eventually walked before the next batter, Norris, hit his second two-out home run of the day.

"Just couldn't find the strike zone," Gonzalez said. "Mistake pitches, left them up in the zone and good hitters made contact."

Kazmir and the A's bullpen did the rest. Joe Savery pitched the eighth and Jim Johnson worked the ninth to complete the seven-hitter.

Before the game, Washington placed first baseman Adam LaRoche on the disabled list with a right quad strain. LaRoche, who has five home runs and 21 RBIs, joins Nationals third baseman Ryan Zimmerman and outfielder Bryce Harper on the DL.

Without its top three hitters, Washington did little offensively.

Kazmir retired the side in order five times in the first six innings, and the Nationals were on the verge of being shut out for the second time in three days until Zach Walters' RBI single off Johnson with two outs in the ninth.

Game notes
The Nationals swept a three-game series from Oakland at home in 2005, the only other time the two teams have faced one another. ... Washington called up 1B Tyler Moore from Triple-A Syracuse to replace LaRoche. Moore batted seventh and went 0-for-3. ... RHP Jordan Zimmerman (2-1) carries a 2.92 ERA into his start Monday at Arizona. ... Oakland RHP Jesse Chavez (2-1) pitches the opener against the White Sox and has allowed one earned run or fewer in five of his seven starts.